Effect of pulse scheme on the microstructural evolution, residual stress state and mechanical performance of resistance spot welded DP1000-GI steel

Abstract

In the present study, the effect of resistance spot welding scheme (i.e. single and double pulse welding) on the mechanical behaviour of resistance spot-welded DP1000-GI steel is investigated. It is shown that double pulse welding at low welding current decreases the maximum crosstension strength and mechanical energy absorption capability of the welds. The factors that lead to the lower mechanical performance of double pulse welds are scrutinised. Local residual stress mapping reveals that the compressive residual stress perpendicular to the plane of the pre-crack either decreases or is fully released at the weld edge of double pulse welds. Orientation imaging microscopy analyses show that the martensite formed in front of the pre-crack of double pulse weld has a lower fraction of high-angle grain boundaries and a coarser structure of Bain groups as opposed to the corresponding area of single pulse weld. Lower mechanical performance of double pulse welds produced at lower welding current is ascribed to the lower compressive residual stress normal to the plane of crack and the formation of martensitic structure in front of the pre-crack with a lower fraction of high-angle grain boundaries and coarser Bain groups.

Effect of Double Pulse Resistance Spot Welding Process on 15B22 Hot Stamped Boron Steel

“…Conversely, the one-step RSW has a narrower PMZ. Chabok et al [20] reported that the two-step RSW has two effects on the property of the PMZ. First, the higher heat input would reduce the residual stress of the PMZ and eliminates the compressive stress perpendicular to the plane of the crack.…”

УПРАВЛЕНИЕ СКОРОСТЬЮ КРИСТАЛЛИЗАЦИИ В УСЛОВИЯХ КОНТАКТНОЙ ТОЧЕЧНОЙ СВАРКИ ПРИ СИНТЕЗЕ СПЛАВОВ Ti–Au

“…Контролировать термические циклы нагрева и охлаждения объема металла литого ядра Уменьшение скорости охлаждения при формировании сплава должно существенно увеличить время пребывания металла в жидком состоянии и обеспечить равномерное распределение золота по всему объему литого ядра, а также привести к снижению остаточных напряжений [11] и уменьшить вероятность образования внутренних дефектов [7]. Управлять скоростью охлаждения в процессе КТС стало возможно с помощью современных источников питания, позволяющих задавать любую форму импульса тока [12,13].…”

Influence of electrode tip diameter on metallurgical and mechanical aspects of spot welded duplex stainless steel

“…Literature demonstrates that mechanical behaviour of spot welded joint is mostly affected by welding current, followed by welding time and electrode force [23]. Furthermore, some process parameters and material conditions such as holding time [24], surface characteristics [25], preheating [26], post heating [27], alloy content [28] and multi pulse [29] are also investigated. However, there is further scope to improve the mechanical performance of spot welded joint by electrode tip diameter.…”